Airflow control for additive manufacturing

ABSTRACT

A method, apparatus, and program for additive manufacturing. The additive manufacturing device includes a positioning mechanism configured to provide independent movement of at least one build unit in at least two dimensions. The build unit may further include a gasflow device for providing a flow zone along a first direction with relation to the build unit. The build unit may further include a powder delivery mechanism and an irradiation beam directing unit. The irradiation bean unit may follow a first irradiation path, wherein the first irradiation path forms at least a first solidification line and at least a second solidification line formed at an angle other than 0° and 180° with respect to the first solidification line. During the formation of the first solidification line, the build unit may be positioned in a first orientation such that the first direction of the flow zone is substantially perpendicular to the first solidification line. During the formation of the second solidification line, the build unit may be positioned in a second orientation such that the flow zone along the first direction is substantially perpendicular to the second solidification line.

INTRODUCTION

The disclosure relates to an improved method of controlling airflowwithin an additive manufacturing apparatus.

BACKGROUND

Additive manufacturing (AM) techniques may include electron beamfreeform fabrication, laser metal deposition (LMD), laser wire metaldeposition (LMD-w), gas metal arc-welding, laser engineered net shaping(LENS), laser sintering (SLS), direct metal laser sintering (DMLS),electron beam melting (EBM), powder-fed directed-energy deposition(DED), and three dimensional printing (3DP), as examples. AM processesgenerally involve the buildup of one or more materials to make a net ornear net shape (NNS) object in contrast to subtractive manufacturingmethods. Though “additive manufacturing” is an industry standard term(ASTM F2792), AM encompasses various manufacturing and prototypingtechniques known under a variety of names, including freeformfabrication, 3D printing, rapid prototyping/tooling, etc. AM techniquesare capable of fabricating complex components from a wide variety ofmaterials. Generally, a freestanding object can be fabricated from acomputer aided design (CAD) model. As an example, a particular type ofAM process uses an energy beam, for example, an electron beam orelectromagnetic radiation such as a laser beam, to sinter or melt apowder material and/or wire-stock, creating a solid three-dimensionalobject in which a material is bonded together.

Selective laser sintering, direct laser sintering, selective lasermelting, and direct laser melting are common industry terms used torefer to producing three-dimensional (3D) objects by using a laser beamto sinter or melt a fine powder. For example, U.S. Pat. No. 4,863,538and U.S. Pat. No. 5,460,758 describe conventional laser sinteringtechniques. More specifically, sintering entails fusing (agglomerating)particles of a powder at a temperature below the melting point of thepowder material, whereas melting entails fully melting particles of apowder to form a solid homogeneous mass. The physical processesassociated with laser sintering or laser melting include heat transferto a powder material and then either sintering or melting the powdermaterial. Electron beam melting (EBM) utilizes a focused electron beamto melt powder. These processes involve melting layers of powdersuccessively to build an object in a metal powder.

AM techniques, examples of which are discussed above and throughout thedisclosure, may be characterized by using a laser or an energy source togenerate heat in the powder to at least partially melt the material.Accordingly, high concentrations of heat are generated in the finepowder over a short period of time. The high temperature gradientswithin the powder during buildup of the component may have a significantimpact on the microstructure of the completed component. Rapid heatingand solidification may cause high thermal stress and cause localizednon-equilibrium phases throughout the solidified material. Further,since the orientation of the grains in a completed AM component may becontrolled by the direction of heat conduction in the material, thescanning strategy of the laser in an AM apparatus and technique becomesan important method of controlling microstructure of the AM builtcomponent. Controlling the scanning strategy in an AM apparatus isfurther crucial for developing a component free of material defects,examples of defects may include lack of fusion porosity and/or boilingporosity.

FIG. 1 is schematic diagram showing a cross-sectional view of anexemplary conventional system 110 for direct metal laser sintering(DMLS) or direct metal laser melting (DMLM). The apparatus 110 buildsobjects, for example, the part 122, in a layer-by-layer manner (e.g.layers L1, L2, and L3, which are exaggerated in scale for illustrationpurposes) by sintering or melting a powder material (not shown) using anenergy beam 136 generated by a source such as a laser 120. The powder tobe melted by the energy beam is supplied by reservoir 126 and spreadevenly over a build plate 114 using a recoater arm 116 travelling indirection 134 to maintain the powder at a level 118 and remove excesspowder material extending above the powder level 118 to waste container128. The energy beam 136 sinters or melts a cross sectional layer (e.g.layer L1) of the object being built under control of the galvo scanner132. The build plate 114 is lowered and another layer (e.g. layer L2) ofpowder is spread over the build plate and object being built, followedby successive melting/sintering of the powder by the laser 120. Theprocess is repeated until the part 122 is completely built up from themelted/sintered powder material. The laser 120 may be controlled by acomputer system including a processor and a memory. The computer systemmay determine a scan pattern for each layer and control laser 120 toirradiate the powder material according to the scan pattern. Afterfabrication of the part 122 is complete, various post-processingprocedures may be applied to the part 122. Post processing proceduresinclude removal of excess powder, for example, by blowing or vacuuming,machining, sanding or media blasting. Further, conventional postprocessing may involve removal of the part 122 from the buildplatform/substrate through machining, for example. Other post processingprocedures include a stress release process. Additionally, thermal andchemical post processing procedures can be used to finish the part 122.

The abovementioned AM processes is controlled by a computer executing acontrol program. For example, the apparatus 110 includes a processor(e.g., a microprocessor) executing firmware, an operating system, orother software that provides an interface between the apparatus 110 andan operator. The computer receives, as input, a three dimensional modelof the object to be formed. For example, the three dimensional model isgenerated using a computer aided design (CAD) program. The computeranalyzes the model and proposes a tool path for each object within themodel. The operator may define or adjust various parameters of the scanpattern such as power, speed, and spacing, but generally does notprogram the tool path directly. One having ordinary skill in the artwould fully appreciate the abovementioned control program may beapplicable to any of the abovementioned AM processes. Further, theabovementioned computer control may be applicable to any subtractivemanufacturing or any pre or post processing techniques employed in anypost processing or hybrid process.

The above additive manufacturing techniques may be used to form acomponent from stainless steel, aluminum, titanium, Inconel 625, Inconel718, Inconel 188, cobalt chrome, among other metal materials or anyalloy. For example, the above alloys may include materials with tradenames, Haynes 188®, Haynes 625®, Super Alloy Inconel 625™, Chronin® 625,Altemp® 625, Nckevac® 625, Nicrofer®6020, Inconel 188, and any othermaterial having material properties attractive for the formation ofcomponents using the abovementioned techniques.

In the abovementioned example, a laser and/or energy source is generallycontrolled to form a series of solidification lines (hereinafterinterchangeably referred to as hatch lines, solidification lines andraster lines) in a layer of powder based on a pattern. A pattern may beselected to decrease build time, to improve or control the materialproperties of the solidified material, to reduce stresses in thecompleted material, and/or to reduce wear on the laser, and/orgalvanometer scanner and/or electron-beam. Various scanning strategieshave been contemplated in the past, and include, for example, chessboardpatters and/or stripe patterns.

One attempt at controlling the stresses within the material of the builtAM component involves the rotation of stripe regions containing aplurality of adjoining parallel vectors, as solidification lines, thatrun perpendicular to solidification lines forming the boundaries of thestripe region for each layer during an AM build process. Parallelsolidification lines, bounded by and perpendicular to a stripe, arerotated for each layer of the AM build. One example of controlling thescanning strategy in an AM apparatus is disclosed in U.S. Pat. No.8,034,279 B2 to Dimter et al., titled “Method and Device forManufacturing a Three-dimensional Object,” which is hereby incorporatedby reference in its entirety.

FIGS. 2 and 3 represent the abovementioned rotating stripe strategy. Thelaser is scanned across the surface of a powder to form a series ofsolidification lines 213A, 213B. The series of solidification lines forma layer of the build and are bound by solidification lines in the formof stripes 211A, 212A and 211B, 212B that are perpendicular to thesolidification lines 213A and 213B forming the boundaries of each striperegion. The stripe regions bounded by solidification lines 211A and 212Aform a portion of a larger surface of the layer to be built. In forminga part, a bulk of the part cross section is divided into numerous striperegions (regions between two solidified stripes containing transversesolidification lines). A stripe orientation is rotated for each layerformed during the AM build process as shown in FIGS. 2 and 3. A firstlayer may be formed with a series of parallel solidification lines 213A,in a stripe region, formed substantially perpendicular to and bounded bysolidified stripes 211A. In a subsequent layer formed over the firstlayer, the stripes 211B are rotated as shown in FIG. 3. By creating astripe boundary for the solidified lines 213A and 213B through a set ofsolidified stripes 211B and 212B that are rotated with respect to theprevious layer, solidification lines 213B, which are be formedperpendicular to and are bounded by stripes 211B are also be rotatedwith respect the solidification lines 213A of the previous layer.

Typical powder bed AM machines require constant gas flow at the area ofmaterial melting and/or sintering. The process chamber in theabovementioned AM apparatus is usually connected to a protective gascircuit through which a protective gas may be supplied to the processchamber in order to establish a protective gas atmosphere within theprocess chamber. The protective gas circuit generally further includes adischarge, area through which gas containing particulate impurities suchas, for example, residual raw material powder particles and weldingsmoke particles may be withdrawn from the process chamber.

Keeping the airflow in a specific orientation with relation to theabovementioned solidification lines is advantageous in producingconstant metallurgy of the AM built component. For example, US Pat. App.Pub. 2014/0301883 A1, to Wiesner et al., titled “Method and Apparatusfor Producing Three-dimensional Work Pieces,” which is herebyincorporated by reference in its entirety, discloses a need to controlthe gas flow within an AM apparatus with respect to the abovementionedsolidification lines. In the abovementioned '883 application, the AMapparatus is controlled such that the angle with respect to a directionof flow of a gas stream flowing across the build surface extends at anangle between 0° and 90° or between 270° and 360°. However, because theairflow direction is fixed most AM apparatuses, maintaining thedirection of gas flow with respect to the solidification lines wouldinvolve determining an acceptable angular range between the formation ofsolidification lines and the gas flow and only forming solidificationlines in an orientation that is within an angular range that isacceptable with relation to the gas flow provided. This greatly limitsthe angular variation of the solidification lines being formed in eachlayer, thus limiting the ability to control the microstructure of thecompleted component.

it is necessary to vary the direction of the gas flow 290 which greatlyincreases the complexity of the AM apparatus. Further, the variationresults in delays which increase build time. Another method ofmaintaining the direction of gas flow with respect to the solidificationlines would involve determining an acceptable angular range between theformation of solidification lines and the gas flow and only formingsolidification lines 213A, and/or 213B in an orientation that is withinan angular range that is acceptable with relation to the gas flowprovided.

For at least the above reasons, a need exists to control the gas flowacross the build surface with relation to the solidification lines beingformed while building an AM component.

SUMMARY OF THE INVENTION

In one aspect, an additive manufacturing device is disclosed, whereinthe additive manufacturing device include a positioning mechanismconfigured to provide independent movement of at least one build unit inat least two dimensions. The build unit may further include a gasflowdevice for providing a flow zone along a first direction with relationto the build unit. The build unit may further include a powder deliverymechanism and an irradiation beam directing unit. The irradiation beanunit may follow a first irradiation path, wherein the first irradiationpath forms at least a first solidification line and at least a secondsolidification line formed at an angle other than 0° and 180° withrespect to the first solidification line. During the formation of thefirst solidification line, the build unit may be positioned in a firstorientation such that the first direction of the flow zone issubstantially perpendicular to the first solidification line. During theformation of the second solidification line, the build unit may bepositioned in a second orientation such that the flow zone along thefirst direction is substantially perpendicular to the secondsolidification line.

The build unit may be rotatably mounted to the positioning system aboutan axis substantially perpendicular to the first direction and may berotated from the first orientation to the second orientation. Theabovementioned apparatus may further include a mobile platform that isconfigured to move independently of the build unit. For example, thebuild platform may be rotatable about an axis.

A method for manufacturing an object is further disclosed. The methodmay include the positioning of a build unit with a mechanism configuredto provide independent movement of at least one build unit in at leasttwo dimensions. The build unit may further include at least one gas flowdevice capable of providing a gas flow zone along a first direction withrelation to the build unit. The method may further include irradiating apowder along a first irradiation path to form a first solidificationline at least partially at a first angle and irradiating a powder alonga second irradiation path to form a second solidification line at leastpartially at an angle other than 0° and 180° with respect to the firstsolidification line. During the formation of the first solidificationline the build unit may be positioned such that the first direction ofthe flow zone is substantially perpendicular to the first solidificationline. During the formation of the second solidification line the buildunit may be positioned such that the flow zone along the first directionis substantially perpendicular to the second solidification line.

A non-transitory computer readable medium storing a program configuredto cause a computer to execute an additive manufacturing process usingan additive manufacturing apparatus is further disclosed. The additivemanufacturing process may comprise forming at least one firstsolidification line. A gasflow device may be positioned in a firstorientation such that the flow zone is along a first direction that issubstantially perpendicular to the first solidification line. Theprogram may further be configured to control the additive manufacturingapparatus form at least a second solidification line formed at an angleother than 0° and 180° with respect to the first solidification line.The gasflow device may be re-positioned to a second orientation suchthat the flow zone is substantially perpendicular to the secondsolidification line.

Further, in any of the abovementioned aspects or disclosure herewith,any number of build units may be used in parallel, i.e. substantiallysimultaneously, to build one or more object(s) and/or build envelope(s),all on the same work surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more example aspects ofthe present disclosure and, together with the detailed description,serve to explain their principles and implementations.

FIG. 1 is a side view diagram of a conventional additive manufacturingtechnique used to form at least part of a component;

FIG. 2 is a top view depicting a conventional hatch and stripe patternused to form at least a part of a component;

FIG. 3 is a top view depicting a conventional hatch and stripe patternused to form at least a part of a component;

FIG. 4 is a perspective view, depicting example layers of componentbuild during a conventional AM process;

FIG. 5 is a top view depicting a hatch and stripe pattern used to formeach layer of the component depicted in FIG. 4 and the gas flowdirection in accordance with one aspect of the disclosure;

FIG. 6 is a side view cross section of a build unit in accordance withone aspect of the disclosure;

FIG. 7 is a side view cross section of a build unit and part of therotating build platform of an additive manufacturing apparatus inaccordance with one aspect of the disclosure;

FIG. 8 is a top view depicting example orientations of the build unit inaccordance with one aspect of the disclosure;

FIG. 9 is a perspective view of the apparatus in FIG. 6, showing exampleorientations of the build unit in accordance with one aspect of thedisclosure;

FIG. 10 is a perspective view of the apparatus in FIG. 7, showingexample orientations of the build unit in accordance with one aspect ofthe disclosure.

DETAILED DESCRIPTION

While the aspects described herein have been described in conjunctionwith the example aspects outlined above, various alternatives,modifications, variations, improvements, and/or substantial equivalents,whether known or that are or may be presently unforeseen, may becomeapparent to those having at least ordinary skill in the art.Accordingly, the example aspects, as set forth above, are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the disclosure. Therefore, thedisclosure is intended to embrace all known or later-developedalternatives, modifications, variations, improvements, and/orsubstantial equivalents.

When using any of the abovementioned AM techniques to form a part by atleast partially melting a powder, a scan of the laser across the powdermaterial, in a raster scan fashion is used to create hatch scans(hereinafter referred to interchangeably as hatch scans, rasters, scanlines, or solidification lines). During an AM build, the abovementionedsolidification lines are used to form the bulk of a part cross section.Contour scans, may further be used to outline the edges of the partcross section. During a raster scan process, the energy source or laseris turned on, increased in power and/or focused in regions where a solidportion of the AM build is desired, and switched off, defocused, and/ordecreased in power where melt formation of the object's cross section inthat layer are not desired. During a raster scan process, at leastpartially melting of powder and formation of solidification is repeatedalong adjacent solidification lines, for example, to form a singlemelted and fused cross section of the object to be built, while thecontour scans create a discrete border or edge of the part. In theexample AM apparatus using a powder bed, once the melt formation of onecross section of the object being built is completed, the apparatuscoats the completed cross-sectional surface with an additional layer ofpowder. The process is repeated until the object is complete.

For the above reasons, the laser and/or energy source is controlled toform a series of solidification lines in a layer of powder using apattern for at least the following reasons; to decrease build time, tocontrol the heat buildup within the powder and/or to increase theefficiency of the build, to improve and/or control the materialproperties of the solidified material, to reduce stresses in thecompleted material, and/or to reduce wear on the laser and/orgalvanometer scanner.

As shown in FIGS. 4 and 5, a built AM component includes a plurality oflayers 215, 216, 217. One example of the abovementioned strategy isshown, for example, a first layer 217 may be divided by software intoseveral stripe regions bounded by, stripes 257 and 277 formed assolidification lines. The stripes 257 and 277 may form a boundary forindividually formed parallel adjoining vectors or solidification lines267. The surface of the part includes a plurality of stripes coveringthe surface to be built. As shown in FIG. 5, each stripe region isbounded by solidified stripes 257 and 277 in layer 217 form a boundaryfor a series of parallel solidified lines 267. The parallelsolidification lines 267 are perpendicular to the solidified stripeboundaries 257 and 277. The stripes are oriented at a first angle inlayer 217 with the perpendicular solidification lines 267 being formedsubstantially perpendicular to the stripes 257 and 277. The striperegion bound by solidified stripes 256 and 257 on a second layer 216 areangled with respect to the solidified stripe boundaries 257 and 277 onprevious layer 217. Accordingly, solidification lines 266 that runperpendicular to solidified stripes 256 and 276 are also be angled withrespect to the solidification lines 267 on previous layer 217. As thebuild progresses, a next layer having stripes 265 and 275 on a thirdlayer 215 are angled with respect to stripes 257 and 277 on layer 217;and stripes 256 and 276 on layer 216.

Additional details for scan strategies that can be used in accordancewith the present invention may be found in U.S. patent application Ser.No. 15/451,108, titled “Triangle Hatch Pattern for AdditiveManufacturing,” with attorney docket number 037216.00070, and filed Mar.7, 2017; U.S. patent application Ser. No. 15/451043, titled “LegElimination Strategy for Hatch Pattern,” with attorney docket number037216.00078, and filed Mar. 6, 2017; U.S. patent application Ser. No.15/459,941, titled “Constantly Varying Hatch for AdditiveManufacturing,” with attorney docket number 037216.00077, and filed Mar.15, 2017, the disclosures of which are incorporated herein by reference.

For the best possible build environment, powder bed additivemanufacturing machines require constant gas flow at the area of materialmelting and/or sintering. The process chamber in the abovementioned andbelow mentioned AM apparatus is usually connected to a protective gascircuit through which a protective gas may be supplied to the processchamber in order to establish a protective gas atmosphere within theprocess chamber. The protective gas circuit generally further includes adischarge area through which gas containing particulate impurities suchas, for example, residual raw material powder particles and weldingsmoke particles may be withdrawn from the process chamber. Using theapparatuses and methods discussed herein, it is possible to provide gasflow 290A-C in the desired orientation with respect to thesolidification lines 255, 266, and 267, for example. As shown in FIG, 5,the below mentioned apparatuses and methods allow the gas flow directionto be controlled for each layer 217, 216 and 215 during the AM build.For example, a build unit (discussed below) may be positioned such thatthe gas flow 290C is substantially perpendicular to the solidificationlines 267 being formed in layer 217. Once layer 217 is completed, powderis provided to the desired regions and layer 216 is formed with thebuild unit in such an orientation that the gas flow 290B issubstantially perpendicular to solidification lines 266. Similarly, oncelayer 216 is completed, powder is provided to the desired regions andlayer 217 is formed with the build unit in such an orientation that thegas flow 290C is substantially perpendicular to solidification lines255. While throughout the disclosure, the gas flow region may bereferred to as substantially perpendicular, it is noted that thedisclosure is not limited as such. For example it may be desirable tohave the gas flow in another angle besides ninety degrees with respectto the solidification lines without departing from the scope of thedisclosure.

FIG. 6 shows an example of one embodiment of a large-scale AM apparatusaccording to the present invention. The apparatus comprises apositioning system (not shown), a build unit 400 comprising anirradiation emission directing device 401, a laminar gas flow zone 404,and a build plate (not shown) beneath an object being built 415. Themaximum build area is defined by the positioning system (not shown),instead of by a powder bed as with conventional systems, and the buildarea for a particular build can be confined to a build envelope 414 thatmay be dynamically built up along with the object. In general, thepositioning system used in the present invention may be anymultidimensional positioning system such as a gantry system, a deltarobot, cable robot, robot arm, etc. The irradiation emission directingdevice 401 may be independently moved inside of the build unit 400 by asecond positioning system (not shown). The atmospheric environmentoutside the build unit, i.e. the “build environment,” or “containmentzone,” may be controlled such that the oxygen content is reducedrelative to typical ambient air, and so that the environment is atreduced pressure. In some embodiments, the recoater used is a selectiverecoater. One embodiment of a selective recoater 411 is illustrated inFIG. 6.

There may also be an irradiation source that, in the case of a lasersource, originates the photons comprising the laser irradiation that isdirected by the irradiation emission directing device. When theirradiation source is a laser source, then the irradiation emissiondirecting device may be, for example, a galvo scanner, and the lasersource may be located outside the build environment. Under thesecircumstances, the laser irradiation may be transported to theirradiation emission directing device by any suitable means, forexample, a fiber-optic cable. When the irradiation source is an electronsource, then the electron source originates the electrons that comprisethe e-beam that is directed by the irradiation emission directingdevice. When the irradiation source is an electron source, then theirradiation emission directing device may be, for example, a deflectingcoil. When a large-scale additive manufacturing apparatus according toan embodiment of the present invention is in operation, if theirradiation emission directing devices directs a laser beam, thengenerally it is advantageous to include a gasflow device 404 providingsubstantially laminar gas flow 403B zone. As shown in FIG. 6, the flowdirection is represented by arrows 403B which in the example shown inFIG. 6 represents a flow along the X direction. An electron-beam mayalso be used in instead of the laser or in combination with the laser.An e-beam is a well-known source of irradiation. For example, U.S. Pat.No. 7,713,454 to Larsson titled “Arrangement and Method for Producing aThree-Dimensional Product” (“Larsson”) discusses e-beam systems, and isincorporated herein by reference.

The gasflow device 404 may provide gas to a pressurized outlet portion(not shown) and a vacuum inlet portion (not shown) which may provide gasflow in a direction 403B to a gasflow zone 403, and a recoater 405.Above the gasflow zone 404 there is an enclosure 418 which may containan inert environment 419. The recoater 405 may include a hopper 406comprising a back plate 407 and a front plate 408. The recoater 405 alsohas at least one actuating element 409, at least one gate plate 410, arecoater blade 411, an actuator 412, and a recoater arm 413. Therecoater is mounted to a mounting plate 420. FIG. 6 also shows a buildenvelope 414 that may be built by, for example, additive manufacturingor Mig/Tig welding, an object being formed 415, and powder 416 containedin the hopper 405 used to form the object 415. In this particularexample, the actuator 412 activates the actuating element 409 to pullthe gate plate 410 away from the front plate 408. In an embodiment, theactuator 412 may be, for example, a pneumatic actuator, and theactuating element 409 may be a bidirectional valve. In an embodiment,the actuator 412 may be, for example, a voice coil, and the actuatingelement 409 may be a spring. There is also a hopper gap 417 between thefront plate 408 and the back plate 407 that allows powder to flow when acorresponding gate plate is pulled away from the powder gate by anactuating element. The powder 416, the back plate 407, the front plate408, and the gate plate 410 may all be the same material. Alternatively,the back plate 407, the front plate 408, and the gate plate 410 may allbe the same material, and that material may be one that is compatiblewith any desired material, such as cobalt-chrome for example. In thisparticular illustration of one embodiment of the present invention, thegas flow in the gasflow zone 404 flows in the x direction, but couldalso flow in any desired direction with respect to the build unit. Therecoater blade 411 has a width in the x direction. The direction of theirradiation emission beam when θ₂ is approximately 0 defines the zdirection in this view. The gas flow in the gasflow zone 404 may besubstantially laminar. The irradiation emission directing device 401 maybe independently movable by a second positioning system (not shown).This illustration shows the gate plate 410 in the closed position.

Further it is noted that while the abovementioned selective powderrecoating mechanism 405 only includes a single powder dispenser, thepowder recoating mechanism may include multiple compartments containingmultiple different material powders are also possible.

When the gate plate 410 in the open position, powder in the hopper isdeposited to make fresh powder layer 521, which is smoothed over by therecoater blade 511 to make a substantially even powder layer. In someembodiments of the present invention, the substantially even powderlayer may be irradiated at the same time that the build unit is moving,which would allow for continuous operation of the build unit and thusfaster production of the object.

FIG. 7 shows a side view of a manufacturing apparatus 300 includingdetails of the build unit 302, which is pictured on the far side of thebuild platform. The mobile build unit 302 includes an irradiation beamdirecting mechanism 506, a gas-flow mechanism 532 with a gas inlet andgas outlet (not shown) providing gas flow to a gas flow zone indirection 538, and a powder recoating mechanism 504. In this example,the flow direction is represented by arrow heads 538, which in theexample shown in FIG. 7 represents a flow along the X direction. Abovethe gas flow zone 538, there may be an enclosure 540 that contains aninert environment 542. The powder recoating mechanism 504, which ismounted on a recoater plate 544, has a powder dispenser 512 thatincludes a back plate 546 and a front plate 548. The powder recoatingmechanism 504 also includes at least one actuating element 552, at leastone gate plate 516, a recoater blade 550, an actuator 518 and a recoaterarm 508. In this embodiment, the actuator 518 activates the actuatingelement 552 to pull the gate plate 516 away from the front plate 548, asshown in FIG. 7. There is also a gap 564 between the front plate 548 andthe gate plate 516 that allows the powder to flow onto the rotatingbuild platform 310 when the gate plate 516 is pulled away from the frontplate 548 by the actuating element 552.

FIG. 7 shows a build unit 302 with the gate plate 516 at an openposition. The powder 515 in the powder dispenser 512 is deposited tomake a fresh layer of powder 554, which is smoothed over a portion ofthe top surface (i.e. build or work surface) of the rotating buildplatform 310 by the recoater blade 510 to make a substantially evenpowder layer 556 which is then irradiated by the irradiation beam 558 toa fused layer that is part of the printed object 330. In someembodiments, the substantially even powder layer 556 may be irradiatedat the same time as the build unit 302 is moving, which allows for acontinuous operation of the build unit 302 and hence, a moretime-efficient production of the printed or grown object 330. The objectbeing built 330 on the rotating build platform 310 is shown in a powderbed 314 constrained by an outer build wall 324 and an inner build wall326. In this particular illustration of one embodiment of the presentinvention, the gas flow in the gasflow zone 532 flows in the xdirection, but could also flow in any desired direction with respect tothe build unit.

It is noted that while the abovementioned selective powder recoatingmechanism 504 only includes a single powder dispenser, the powderrecoating mechanism may include multiple compartments containingmultiple different material powders are also possible.

Additional details for a build units and positioning mechanisms for asingle and/or multiple units that can be used in accordance with thepresent invention may be found in U.S. patent application Ser. No.15/610,177, titled “Additive Manufacturing Using a Mobile Build Volume,”with attorney docket number 037216.00103, and filed May, 31, 2017; U.S.patent application Ser. No. 15/609,965, titled “Apparatus and Method forContinuous Additive Manufacturing,” with attorney docket number037216.00102, and filed May 31, 2017; U.S. patent application Ser. No.15/610,113, titled “Method for Real-Time Simultaneous Additive andSubtractive Manufacturing With a Dynamically Grown Build Wall,” withattorney docket number 037216.00108, and filed May 31, 2017; U.S. patentapplication Ser. No. 15/610,214, titled “Method for Real-TimeSimultaneous and Calibrated Additive and Subtractive Manufacturing,”with attorney docket number 037216.00109, and filed May 31, 2017; U.S.patent application Ser. No. 15/609,747, titled “Apparatus and Method forReal-Time Simultaneous Additive and Subtractive Manufacturing withMechanism to Recover Unused Raw Material,” with attorney docket number037216.00110, and filed May 31, 2017; U.S. patent application Ser. No.15/406,444, titled “Additive Manufacturing Using a Dynamically GrownBuild Envelope,” with attorney docket number 037216.00061, and filedJan. 13, 2017; U.S. patent application Ser. No. 15/406,467, titled“Additive Manufacturing Using a Mobile Build Volume,” with attorneydocket number 037216.00059, and filed Jan. 13, 2017; U.S. patentapplication Ser. No. 15/406,454, titled “Additive Manufacturing Using aMobile Scan Area,” with attorney docket number 037216.00060, and filedJan. 13, 2017; U.S. patent application Ser. No. 15/406,461, titled“Additive Manufacturing Using a Selective Recoater,” with attorneydocket number 037216.00062, and filed Jan. 13, 2017; U.S. patentapplication Ser. No. 15/406,471, titled “Large Scale Additive Machine,”with attorney docket number 037216.00071, and filed Jan. 13, 2017, thedisclosures of which are incorporated herein by reference.

As mentioned above with respect to the example solidification lineorientations shown in FIGS. 4 and 5, with respect to the above-mentionedAM apparatuses, as the angle of the solidification lines (e.g. 255, 266,and/or 267) of each layer 215-217 is varied, the mobile build units inthe abovementioned manufacturing apparatuses is oriented so as to allowthe desired gas flow direction and solidification line orientation.

FIG. 8 shows an example of a gas flow orientation control according toone aspect of the disclosure. For example, a single layer (e.g. as shownin FIG. 4) may be formed with solidification lines formed in a firstorientation 606. In this example, a simplified version any of theabovementioned build units is shown as reference 616A. When building acomponent 610 using an AM process, a build 616A may be moved to a firstlocation to form solidification lines 606A. The build unit 616A may beoriented at the first location such that the gas flow is in direction608A which may be substantially perpendicular to the solidificationlines 606A being formed. In a second layer (e.g. L2 shown in FIG. 4), itmay be desirable to form the solidification lines 606B in a secondorientation different from the orientation used to form solidificationlines 606A. A build may move via path 612 to form at least a portion ofthe component 610 using solidification lines 606B and the build unit maybe oriented in a position 616B such that the gas flow direction 608B issubstantially perpendicular to the solidification lines 606B beingformed. Similarly, in a third layer (e.g. L3 in shown in FIG. 4), it maybe desirable to form the solidification lines 606C in a secondorientation different from the orientation used to form solidificationlines 606B. A build unit may move via path 614 to form at least aportion of the component 610 using solidification lines 606C and thebuild unit may be oriented in a position 616C such that the gas flowdirection 608C is substantially perpendicular to the solidificationlines 606C being formed. It is noted that while the abovementionedexample discusses the solidification lines 606A-C being a variation witheach layer (e.g. L1-L3 as shown in FIG. 4), the solidification lines606A-C may also be varied while forming a single layer. In other wordseach of the solidification lines 606A-C and orientations of the buildunit and gas flow directions 608A-B, respectively, may occur in a singlelayer (e.g. only layer L1, L2, and/or L3 shown in FIG. 4). It is furthernoted that the locations and orientations shown in FIG. 8, as well asall the figures disclosed, are only shown as examples, one havingordinary skill in the art would understand that any orientation and/orsolidification lines and/or series of orientations are possible based onthe current disclosure. Further, it is noted that multiple build unitsmay be used simultaneously to further improve build speed.

FIG. 9 is a perspective view of an example application of the disclosedinvention. For example, the gas flow control of the current disclosuremay be applicable to a mobile build unit 802 for forming an AM component810 within a grown build envelope 818 for containing powder 813 appliedduring the build process. A single layer (e.g. as shown in FIG. 4) maybe formed with solidification lines formed in a first orientation 806A.In this example, a simplified version any of the abovementioned buildunits is shown as reference 802. When building a component 810 using anAM process, a build 802 may be moved to a first location and orientation816A to form solidification lines 806A. The build unit 802 may beoriented at the first location 816A such that the gas flow zone 803 ispositioned such that the gas flow is in direction 808A which may besubstantially perpendicular to the solidification lines 806A beingformed. In a second layer (e.g. L2 shown in FIG. 4), it may be desirableto form the solidification lines 806B in a second orientation differentfrom the orientation used to form solidification lines 806A. A build maymove via path 812 and rotate in direction R to form at least a portionof the component 810 using solidification lines 806B and the build unitmay be oriented in a position 816B such that the gas flow direction 808Bis substantially perpendicular to the solidification lines 806B beingformed. It is noted that while the abovementioned example discusses thesolidification lines 806A-B being varied within each layer (e.g. L1-L2as shown in FIG. 4), the solidification lines 806A-B may also be variedwhile forming a single layer. In other words each of the solidificationlines 806A-B and orientations of the build unit and gas flow directions808A-B, respectively, may occur in a single layer (e.g. only layer L1,L2, and/or L3 shown in FIG. 4). It is further noted that the locationsand orientations shown in FIG. 9, as well as all the figures disclosed,are only shown as examples, one having ordinary skill in the art wouldunderstand that any orientation and/or solidification lines and/orseries of orientations are possible based on the current disclosure.Further, it is noted that multiple build units may be usedsimultaneously to further improve build speed.

FIG. 10 is a perspective view of an example application of the disclosedinvention. For example, the gas flow control of the current disclosuremay be applicable to a mobile build unit 902 for forming an AM component910 on a mobile build platform 910. The AM component 910 may be builtwithin a grown build envelope and/or a build envelope 818 for containingpowder 813 applied during the build process. In FIG. 10, forsimplification of the figures, the build unit 902 is shown in a singlelocation, however the build unit may be moved to a location representedby dotted line 916A, 916B, and/or at any location within the apparatus900. Further, it is noted that since a rotatable build platform 910 isused the build unit may stay stationary with respect to the y directionand may simply rotate and move in the z direction and move inward andoutward in a radial direction (x direction shown in FIG. 10). Thus themovement, in conjunction with the rotation of the rotatable platform 910allows the build unit to build a portion of the AM component atvirtually any location within the apparatus 900. Further, it is notedthat the build platform 910 may be movable in the z direction either incombination with or as an alternative to the build unit being movable inthe z direction. In one aspect, for example, the build platform 910 maybe movable in the z direction, while the build unit 901 is rotatable andmovable inward and outward in a radial direction (i.e. x direction asshown in FIG. 10) while being stationary in the z direction. As yetanother example, the build unit 902 may be sufficiently large so thatthe build unit only needs to be rotatable and movable in the zdirection. In other words, if the build unit 902 is sufficiently largeso as to cover the entire width of the radial part being built, thebuild unit may only need to be rotatable so as to vary airflow directionsince the build unit is capable of scanning the build material acrossthe entire width of the part. Further, it is noted that in the aspectmentioned above, the build unit 902 may be movable in each direction(i.e. rotatable, z, x, and y) so that raster scans can be formed in anydirection while the build platform 910 remains stationary. One ofordinary skill would understand that the below mentioned process isapplicable to any single or combination of the above movements forforming an AM component.

A single layer (e.g. as shown in FIG. 4) may be formed withsolidification lines formed in a first orientation 906A. In thisexample, a simplified version any of the abovementioned build units isshown as reference 902. When building a component 910 using an AMprocess, a build 902 may be moved to a first location and orientation916A to form solidification lines 906A. The build unit 902 may beoriented at the first location 916A such that the gas flow zone ispositioned such that the gas flow is in direction 908A which may besubstantially perpendicular to the solidification lines 906A beingformed. In a second layer (e.g. L2 shown in FIG. 4), it may be desirableto form the solidification lines 906B in a second orientation differentfrom the orientation used to form solidification lines 906A. A buildunit may move and/or rotate to form at least a portion of the component810 using solidification lines 906B and the build unit may be orientedin a position 916B such that the gas flow direction 908B issubstantially perpendicular to the solidification lines 906B beingformed. It is noted that while the abovementioned example discusses thesolidification lines 906A-B being a variation with each layer (e.g.L1-L2 as shown in FIG. 4), the solidification lines 906A-B may also bevaried while forming a single layer. In other words each of thesolidification lines 906A-B and orientations of the build unit and gasflow directions 908A-B, respectively, may occur in a single layer (e.g.only layer L1, L2, and/or L3 shown in FIG. 4). It is further noted thatthe locations and orientations shown in FIG. 10, as well as all thefigures disclosed, are only shown as examples, one having ordinary skillin the art would understand that any orientation and/or solidificationlines and/or series of orientations are possible based on the currentdisclosure. Further, it is noted that multiple build units may be usedsimultaneously to further improve build speed.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal language of the claims.Aspects from the various embodiments described, as well as other knownequivalents for each such aspect, can be mixed and matched by one ofordinary skill in the art to construct additional embodiments andtechniques in accordance with principles of this application.

What is claimed is:
 1. A system for producing an additively manufacturedcomponent, the system comprising: a positioning mechanism configured toprovide independent movement of at least one build unit in at least onedimension, the build unit comprising: a gasflow device for providing aflow zone along a first direction with relation to the build unit; apowder delivery mechanism; and an irradiation beam directing unit,wherein the irradiation beam directing unit follows a first irradiationpath, wherein the first irradiation path forms at least a firstsolidification line and at least a second solidification line formed atan angle other than 0° and 180° with respect to the first solidificationline, wherein during the formation of the first solidification line thebuild unit is positioned in a first orientation such that the firstdirection of the flow zone is substantially perpendicular to the firstsolidification line, and during the formation of the secondsolidification line the build unit is positioned in a second orientationsuch that the flow zone along the first direction is substantiallyperpendicular to the second solidification line.
 2. The system forproducing an additively manufactured component of claim 1, wherein thebuild unit is rotatably mounted to the positioning mechanism about anaxis substantially perpendicular to the first direction and is rotatedfrom the first orientation to the second orientation.
 3. The system forproducing an additively manufactured component of claim 2, wherein thepowder delivery mechanism provides powder onto a rotatable buildplatform, wherein the build platform is rotated after the formation ofthe first solidification line.
 4. The system for producing an additivelymanufactured component of claim 1, wherein the gasflow device produces alaminar flow along the first direction.
 5. The system for producing anadditively manufactured component of claim 3, wherein the firstsolidification line comprises a plurality of parallel solidificationlines.
 6. The system for producing an additively manufactured componentof claim 5, wherein the second solidification line comprises a pluralityof parallel solidification lines.
 7. The system for producing anadditively manufactured component of claim 1, wherein the build unitfurther comprises a powder recoater.
 8. The system for producing anadditively manufactured component of claim 6, wherein the series offirst solidification lines are formed on a first layer of powder,wherein the second set of solidification lines are formed on a secondlayer of powder provided over the first layer of powder by the powderdelivery mechanism.
 9. The system for producing an additivelymanufactured component of claim 1, further comprising a mobile buildplatform configured to move independently of the build unit.
 10. Amethod for manufacturing an object comprising: positioning a build unitwith a mechanism configured to provide independent movement of at leastone build unit in at least two dimensions, wherein the build unitincludes at least one gas flow device capable of providing a gas flowzone along a first direction with relation to the build unit;irradiating a powder along a first irradiation path to form a firstsolidification line at least partially at a first angle; irradiating apowder along a second irradiation path to form a second solidificationline at least partially at an angle other than 0° and 180° with respectto the first solidification line, wherein during the formation of thefirst solidification line the build unit is positioned such that thefirst direction of the flow zone is substantially perpendicular to thefirst solidification line, and during the formation of the secondsolidification line the build unit is positioned such that the flow zonealong the first direction is substantially perpendicular to the secondsolidification line.
 11. The method of claim 10, wherein the build unitis rotated from the first orientation to the second orientation about anaxis substantially perpendicular to the first direction.
 12. The methodof claim 10, wherein the gasflow device produces a laminar flow alongthe first direction.
 13. The method of claim 10, wherein irradiation apowder along the first irradiation path comprises forming a plurality ofparallel solidification lines at the first angle.
 14. The method ofclaim 13, wherein irradiation a powder along the second irradiation pathcomprises forming a plurality of parallel solidification lines at thesecond angle.
 15. The method of claim 14, wherein the series of firstsolidification lines are formed on a first layer of powder and thesecond set of solidification lines are formed on a second layer ofpowder provided over the first layer of powder by a powder deliverymechanism.
 16. A non-transitory computer readable medium storing aprogram configured to cause a computer to execute an additivemanufacturing process using an additive manufacturing apparatus, theadditive manufacturing process comprising: forming at least one firstsolidification line, wherein a gasflow device is positioned in a firstorientation such that the flow zone is along a first direction that issubstantially perpendicular to the first solidification line; forming atleast a second solidification line formed at an angle other than 0° and180° with respect to the first solidification line, wherein the gasflowdevice is re-positioned to a second orientation such that the flow zoneis substantially perpendicular to the second solidification line. 17.The program of claim 16, wherein during the execution of the additivemanufacturing process, the additive manufacturing apparatus build unitis controlled to rotate from the first orientation to the secondorientation about an axis substantially perpendicular to the firstdirection.
 18. The program of claim 16, wherein during the execution ofthe additive manufacturing process, the gasflow device is controlled toproduce a laminar flow along the first direction.
 19. The program ofclaim 16, wherein during the execution of the additive manufacturingprocess, an irradiation beam directing unit is controlled to form thefirst solidification line and a plurality of solidification linesparallel to the first solidification line, wherein the irradiation beamdirecting unit is controlled to form the second solidification line anda plurality of solidification lines parallel to the secondsolidification line.
 20. The program of claim 19, wherein the additivemanufacturing apparatus is further controlled to form first series ofsolidification lines on a first layer of powder and the second set ofsolidification lines on a second layer of powder provided over the firstlayer of powder by a powder delivery mechanism.
 21. The program of claim16, wherein the additive manufacturing apparatus is further controlledto rotate a mobile build platform after forming at least one of thefirst solidification line or the second solidification line.